The subject matter of the present invention pertains to means for electronically generating cursors, or other visual position indicators, in a raster-scan type display system to facilitate the identification, entry, modification, or deletion of information at selected locations within a particular area of a display presentation.
The desirability and advantage of an electronically generated cursor that may be positioned within a broad area of a display presentation are well recognized to those persons familiar with the art. Normally, in a raster-scan type display system employed to display alphanumeric information, the cursor takes the form of a small underline segment that is positionable directly below a character location to identify the specific address that is to be affected. The circuitry employed to generate and position the cursor also produces electronic signals representative of the cursor location for use by other sections of the display system in identifying the selected address. In raster-scan type display systems capable of presenting graphic as well as alphanumeric information, the cursor may take other forms, for example that of a small cross, circle, or combination thereof.
The primary disadvantage of known cursor generating systems is that the small cursor symbol produced thereby is difficult to locate and position accurately when the display presentation is overly crowded. This disadvantage is particularly present in a graphics environment where the information forming the display presentation is not as ordered or uniform in appearance as that of an alphanumeric display. A second disadvantage is that symbols such as circles and small crosses are difficult to position precisely because, in the case of the circle, there is no precise indication of an exact center point, and in the case of the cross, the center point itself, although readily discernable, tends to overlay and obscure the data being identified.
Accordingly, there remains a need for means in a display system for generating a graphic cursor that is both easy to see when used in conjunction with a crowded display presentation and easy to position without obscurring the information being identified.